Rethinking 'waste' as power for campus

For student Makayla Mainhood, operations intern with Michigan State University Culinary Services, separating food waste from other materials like plastic and metal is a daily duty. But before her visit to the South Campus Anaerobic Digester, she had no idea that she was actively participating in a much larger process to reduce waste and generate power for campus.

MSU Culinary Services partners with MSU's Anaerobic Digestion Research and Education Center to capture food preparation waste from campus kitchens, such as peels and rinds, for anaerobic digestion. Anaerobic digestion converts organic compounds into biogas, a form of renewable natural gas, in a warm environment without oxygen. Anaerobic digestion takes this material, typically viewed as garbage, and uses it to produce energy for some of the buildings on MSU's south campus.

Material is delivered to the facility daily, the majority being manure from the MSU Dairy Farm, but also in the form of food waste from regional partners, grease from restaurants around the state, biodegradable packing material and food waste from MSU's campus.

Every day, operators add about 20,000 gallons of material to the digester and the process is controlled using temperature and mixing. Microorganisms break down the material retained in the holding tank for 20 to 30 days, and produce biogas as renewable energy. The main goal of the anaerobic digester is forming a closed-loop system: it produces renewable energy while diverting material from the landfill, and - once the energy is used - develops the end byproducts: liquid and solid fertilizers.

MSU is one of only three universities in the United States to have its own self-sustaining anaerobic digester, and it is the largest. However, the majority of students on campus are unaware of both the existence and the purpose of this facility, which has operated since October 2013. "The process of digestion was a surprise, and seeing where the food waste is going and to what it's contributing was definitely an experience," says Mainhood of her visit to the digester, "I wasn't aware of the fact that we can actually use it for energy."

Approximately 10 percent of the energy produced powers the facility itself, and the rest offsets energy production in 10 south campus buildings, generating enough energy to power about 250-300 homes.

The system is very robust, but some challenges result from contamination of the digester. Material that is not organic can damage equipment, and does not produce biogas. Additionally, inorganic material becomes a major problem in the production of fertilizer, as farmers do not want to use liquid digestate or compost containing plastic or metal in their fields or garden.

Mainhood acknowledges some challenges associated with separating food waste. "The biggest struggle is getting people to do it. It's much easier to throw things away," she says of her experience supervising students, "A visit to the digester would make our staff more aware of the importance of preventing plastic or metal material from going to the digester."

While contamination is quite low compared to the successful energy output, operators hope that learning about the facility will make the MSU community more aware of their role in preventing contamination of the waste stream and keeping material out of the landfill.

Carla Iansiti, MSU's Residential Hospitality Sustainability Officer, agrees that understanding the process of anaerobic digestion helps the students working in culinary services establish ownership of their work.

"Our students were amazed by the tour of the digester because they were able to see, and smell, the end impact, and know they are helping to create energy rather than contributing to the landfill. We have information sessions for new hires that are consistent across departments in order to establish a social responsibility and allow them to understand that they are doing more than cooking a hot meal, they are also contributing to a closed food loop."